Grass grub are not alone: using DNA barcoding to identify scarab larvae found in Banks Peninsula, Canterbury

In monetary terms, the native grass grub Costelytra giveni (Coleoptera: Scarabaeidae) has been crowned the most damaging pest to New Zealand’s pastoral industry. However, grass grub is not the only scarab occurring in improved pastures with several other species exhibiting overlapping distributions and similar seasonal life cycles. Examples include the Manuka beetle (Pyronota festiva, Pyronota laeta, Pyronota setosa) and the Tasmanian grass grub (Acrossidius tasmaniae (Coleoptera: Scarabaeidae). All of which can be easily misidentified as each other due to highly similar larval morphology. Accurate identification of the scarab pest larvae is important, as it allows selection of the best management strategy to target the pest species. Whilst pastures infested with grass grub, can be treated with Serratia entomophila (Bioshield), this product is not effective against Manuka beetle. We sampled scarab larvae from several sites on Banks Peninsula and investigated if the mitochondrial cytochrome subunit 1 was a robust method for identifying scarab larvae to species level. The technology allows for a better understanding of species diversity and undertaking management appropriate to the target species.